An over-current protecting has been widely used in manufacturing home appliance and industrial equipment because excessive heating induced by electricity can result into fire. Except for the over-temperature protecting, an over-temperature protection is also needed.
Currently, existing non-resettable thermal fuse used can be sorted into two categories. One category of the thermal fuse uses alloy with low melting point as temperature sensing component. The other category of the thermal fuse uses pressed organic material as a temperature sensing body. A metal elastic clamp contacts with a lead wire electrode through the joining force coming from a compressed compression spring and the temperature sensing body, thus forming a single contact point conductive structure. When the temperature of the environment reaches a pre-set temperature, the temperature sensing body melts. A thin compression spring forces the metal elastic clamp separate from the lead wire electrode, thus cutting off the electric connection. The single contact point conductive structure between the elastic clamp and lead wire electrode has the drawback of high contacting resistance. This conductive structure cannot withstand high current. When surge current flows through the device, a resistance welding would occur and thus disabling the protecting function of the thermal fuse.